Ardea
Official journal of the Netherlands Ornithologists' Union

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Pomeroy D.E. (1978) The biology of Marabou Storks in Uganda. II. Breeding biology and general review. ARDEA 66 (1-2): 1-23
In Uganda, Marabous nest in colonies, mostly with 41-120 pairs (Fig. 2). Breeding was studied in detail at a medium-sized colony near Kampala, with additional observations at about 10 other colonies. Breeding was well-synchronized (Fig. 1). Breeding success apparently depended upon several things. Over a period of years, it increased as the colony grew (Table 3, Fig. 8), presumably be cause birds became more experienced. Experience may also explain the greater success of earlier nests (Table 2, Fig. 4). Further, in a comparison of several colonies and years, success was highest when nests were close together (Fig. 5), and in larger colonies up to a size of about 60 nests, after which it declined (Fig. 3), possibly because birds were having to travel further to find food. In Sudan, much larger colonies occur near to extensive swamps (Table 5), a situation not found in Uganda. Overall breeding success is low, only about one egg in three producing a fledged young. There was a progressive loss of nestlings (Fig. 7). The third nestling, where present, was always the smallest (Fig. 6), but this was because it was several days younger than the first two. However, it was never observed to survive as long as six weeks. The biology of the Marabou is discussed in some detail. Marabous retain most of the morphological characteristics of storks and are also well-adapted to soaring flight, which is particularly important in its scavenging behaviour. Many characteristics .of the 'K-selected species' are exhibited by Marabous, notably with regard to reproduction, where both effort and output seem relatively low. Although K-selected species are typical of stable habitats, and Marabous frequent areas with rather variable rainfall, they can minimize the effects of adverse environmental conditions by movements. In general, seasonal movements follow the rains (Fig. 9).


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